Well, I suspect that, before you get to 250 foot dives, you might have done a number of classes, and possibly not all with the same agency. But I don't think you can lose by beginning with either GUE Fundamentals or UTD Intro to Tech, and I don't even know how to tell you which one to choose. Guy Shockey, the GUE instructor on Vancouver Island, is an extremely nice guy whose motivations and attitude to teaching are fabulous -- I know this because I've been talking to the guy for around three years now.
Todd Powell, the UTD instructor in Vancouver, is also an extremely nice guy who has rapidly built an impressive community there. I went up and dove with them early in January, and I was very impressed with the number of enthusiastic students he has.
Mark Gottfried, the UTD instructor on Vancouver Island, is also an extremely nice man, who was kind enough to come up and visit with us when Peter and I did Saanich Inlet. We didn't dive together, but spent an evening talking about diving, and diving instruction.
I know Guy and Mark are doing the kinds of dives you're talking about, and I know Todd was doing TriMix I dives with my friends the day we dove in Vancouver, so all three are the real meal deal.
Everybody should have that kind of difficult choice to make!